1. Field of Invention
The present invention relates to systems for fluidizing granular materials and more particularly to an expansion joint for connecting fluidized conveyors or fluidized bed sections.
2. Description of the Prior Art
As disclosed in Wentzel et al U.S. Pat. No. 3,870,374, it is well known to transport particulate material such as alumina in a fluidized conveyor. Such a fluidized conveyor is created by flowing a fluid, usually a gas such as air, upwardly through suitably sized solid granular material at a velocity sufficiently high to bouy the granular particles. Fluidization imparts to the bed of granular particles a character similar to that of a liquid.
The longer fluidized conveyors of the prior art slope downwardly at an angle of about 3 to 5 degrees from horizontal. Typically, these conveyors are anchored to the structural support beams in the buildings or to other permanent structures. In such longer conveyors expansion and contraction occurs with changes in temperature. The temperature changes occur frequently due to start and stop conditions with hot and cold granular materials, and due to daily fluctuations in atmospheric temperatures. As the lengths of such conveyors have increased, it has become necessary to provide junctions at certain intervals along the length of the conveyors in order to absorb expansion and contraction between stationary structural support beams and the like.
Junctions of the prior art have consisted primarily of overflow discharge passages which would permit the fluidized material to exit one conveyor section and fall under the influence of gravity downwardly into another conveyor section positioned therebelow and continue the fluidized flow. A similar discharge mechanism is disclosed in Bauer U.S. Pat. No. 2,529,366.
The primary problem with the junctions of the prior art is that the two in-line fluidized conveyors do not maintain their in-line elevation through a junction. For excessively long conveyors of the prior art having more than one such junction, the total elevation drop could be significant enough to cause construction problems. For instance, the hopper that feeds the granular material onto the conveyor may be 25 feet or more in height, and each junction may require an elevation drop of 2 feet or more, and further a downward slope of 3 to 5 degrees for the conveyor may require about 7 feet in elevation for every 100 feet in length. With such elevation changes, it is readily apparent that a significant amount of overhead clearance is required for the longer fluidizing systems of the prior art.
Accordingly, a new and improved junction is required which will absorb expansion, contraction, and all other relative movement of fluidized conveyor and bed sections and not require an elevation differential.